It has been estimated that up to 75% of patients with Systemic Lupus Erythematosus (SLE) experience some type of nervous system manifestations at some point in their disease course. The most common include stroke, cognitive dysfunction and psychiatric disease, although the full range has not been characterized. This five year, prospective study of nervous system disease in SLE patients has as its objectives the characterization of the spectrum of nervous system involvement in an ethnically diverse but predominately Mexican-American population of patients with SLE and the definition of important risk factors which may be unique for specifically targeted nervous system manifestations. Among the study's hypotheses is that the risk of thrombo-occlusive events will be higher in SLE patients who have persistently abnormal levels of aPL and anti-apoH antibodies and that the development of cognitive dysfunction will be temporally associated with abnormal serum levels of these antibodies.